Papers by Keyword: Sonochemistry

Abstract: Synthesis of methylcellulose (MC) using dimethyl carbonate (DMC) with conventional and green methods has been conducted. The cellulose used in this synthesis was obtained from sago waste, which contains 86.67% cellulose. All the methylation products were analyzed using IR and ¹H-NMR spectrometers. The determination of cellulose content was done using TAPPI T-203 method, while the degree of substitution (DS) was based on the Zeisel Method. Conventional synthesis of MC was performed using Na₂HPO₄ (12:1), DMC and NaCl 5% (w/v) (volume ratio = 10:10) at 90 °C. The reaction time was varied (2 to 5 hours); the optimum condition was reached in 3 hours and gave the DS of 1.028. Green synthesis of MC was conducted by employing microwave and sonochemistry techniques. Synthesis MC with the microwave was carried out at the power of 400 W for 200 seconds and gave the DS of 1.036. Synthesis MC with sonochemistry (the variation time 1 to 3 hours) was conducted at the optimum time of 2 hours and gave the DS of 0.646. The DMC volume was also varied (17.5; 20; 22.5; 25; and 30 mL), where the volume ratio of 1:24 gave the highest DS of 1.177. The microwave technique is the best method for synthesis MC compared to conventional and sonochemistry techniques.

Abstract: Hydroxyapatite (HAp) has been synthesized by different techniques, and sonochemical methods have shown to be useful in the HAp nanopartcicles production for biomedical applications such as bone graft substitute. In addition, experimental design is an appropriate tool for planning and evaluating a study to meet specified objectives. Then, this work aimed to synthesize HAp nanosized powders by a sonochemical method and assess the processing parameters via experimental design, in order to obtain dense samples. HAp nanopowders were characterized by X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscope/Field Emission Gun (SEM/FEG). For densification analysis, HAp samples were processed with different parameters, such as: compaction pressure (200 or 400 MPa), sintering temperature (900 or 1100°C), sintering heating rate (2 or 20 °C/min), and sintering time (2 or 4 hours). The samples were analyzed by SEM/FEG, whereas the linear shrinkage and density were considered the response variables for the experimental design. The results indicated that the sonochemical method successfully produced HAp nanoparticles with sphere-like morphology. Further, the experimental design showed that sintering temperature was the variable that most influenced the densification of samples.

Abstract: In this study, nanoparticles La_1-xSr_xFe_0.5Mn_0.25Ti_0.25O₃ particles were prepared by two successive methods: the mechanical alloying (MA) with the successive sintering and the deagglomeration of MA powders in the demineralized water containing surfactant under ultrasonic irradiation. It is shown that MA powders have coarser particle size of a slightly less than 6 micron in average. Additionally, the particle size distribution was relatively broadening which indicates a large size variation in particle sizes. As MA powders were dispersed in the demineralized water and irradiated by a 40 KHz ultrasonic wave for 5 hours the particle size distribution was improve significantly, it has a narrow particle size distribution with a mean particle size almost 180 nm. The particle has crystallite with mean size 20-26 nm subject to XRD line broadening analysis. Thus, the particles can be called nanoparticles clusters. The study also indicated the breakup of nanoparticle cluster was no longer effective in a prolonged ultra sonication time and yet reagglomeration was obvious. However, the latter was not occurred in a disperse media containing surfactants. In this study, four types of surfactant were used and their influences to the particle sizes were evaluated. According to this study, the four types of surfactants could reduce further the particle size but in different pathways. Sodium Dodecyl Sulphate (SDS) as anionic surfactant reduced the sizes of nanoparticle clusters to almost 180 nm by one step ultra sonication. While cationic, non-ionic and amphoteric surfactants promoted the gel formation in the first place, the nanoparticle clusters were then obtained after an additional heating to breaking the gel form to dry powders. The present of gel was due to stabilization process of the particle to avoid any re-agglomeration between each fine particle. In this paper, we discussed a systematic material preparation towards nanoparticles clusters and the mechanism as well as influence of surfactants in particle size reduction for LSMFTO powders.

Abstract: Smart polymers are very important in many fields, such as biochemistry, fine chemicals and functional materials, etc. In this paper, poly (N-isopropyl acrylamide) (PNIPAm) was prepared by ultrasonics sonochemistry. In the reaction system, the monomer is N-isopropyl acrylamide (NIPAm), the crosslinker is N,N'-methylenebisacrylamide (BIS) and the solvent is tetrahydrofuran (THF). FTIR and UV-Vis were used to investigate the chemical constitution and phase transformation property of PNIPAm. The results show that it is successful to obtain PNIPAm. It has thermosensitivity. And its lower critical solution temperature is found to be 34°C. Therefore, a green preparation method for environment-responsive polymer is presented.

Abstract: Room temperature ionic liquids (RTIL) have been developed to a central point of interest in both academia and industry. RTIL is non-volatile, thermally stable and non-flammable solvent. These properties can offer a green opportunity for sonochemical reactions. In this work, the cavitation bubble temperatures have been measured using methyl radical recombination (MRR) method. The temperatures measured in ImPF₆ are in the range of 3000 4000 K. Additionally, based on the bubble dynamic equation with the consideration of liquid surface tension, viscosity and radiative resistance, numerical simulations have been carried out to investigate the cavitation bubble dynamics. The difference of the temperatures obtained from the experiment and numerical simulations has been interpreted.

Abstract: Ropivacaine hydrochloride was synthesized from 2-pipecolic acid by successive reaction with SOCl2 and 2,6-dimethylaniline at 40°C under ultrasonic irradiation to give (S)-N-(2,6-dimethylphenyl)-piperidin-2-carboxamide (4), and 4 was reacted with 1-bromopropane at 50°C for 1 h under ultrasonic irradiation. The effect of reaction solvent, temperature and time under ultrasonic irradiation were investigated. Compared with conventional methods, the main advantages of the present procedure are milder conditions, shorter reaction time and higher yields. The total yield was 63.1%, [α]25 D= – 6.7°(c = 2, H2O).

Abstract: Polymer microcapsules have important application in the fields of biochemistry and materials science owing to their unique structures and functions. Poly(styrene-methyl methacrylate) (PS-co-PMMA) microcapsules were prepared through sonochemical method. The results reveal that it is difficult to form a microcapsule structure from neat styrene (St). However, MMA can improve the interface condition for its higher hydrophilicity. Therefore, it is easier to form hollow structure because polymer microcapsules have a lower interface free energy per unit area. FTIR results confirm that polymer microcapsules have both the typical peaks of PS and PMMA. The results of dynamic light scattering (DLS) and TEM show that PS-co-PMMA microcapsules are uniform in size(about 100 nm in diameter and 20~25 nm in shell thickness).

Abstract: ZnO hierarchical microstructures with uniform sea urchin-like morphology have been successfully synthesized through a facile and reliable ultrasound irradiation route by using Zn(CH3COO)2•2H2O and KOH as raw materials. The ZnO sample is investigated with XRD, SEM, TEM and HRTEM. Results indicate that the as-prepared sea urchin-like ZnO microstructures are assembled by numerous needle-like nanocrystals with the size about 2µm in length and about 100nm in diameter. The preferred growth orientation of these ZnO nanoneedles are along [101] direction. A blue shift in UV-vis absorption spectrum of the as-prepared ZnO sample is observed.

Abstract: Silver nanoparticles were synthesized by a sonochemistry method by using silver stearate and triphenylphosphine as silver precursor and reduction accelerator respectively. The experimental conditions that influence the formation and organization of the particles were investigated, and the particles were characterized by TEM. Results showed that well-ordered two-dimentional (2D)-monolayer was formed after solvent evaporation on a carbon-coated copper TEM grid at the optimal experimental conditions which was that the mole percentage of the amount of reducing agent and triphenylphosphine to silver precursor was 10% and 50% respectively, and the ultrasound power was set at 60% (relative to the maximum ultrasound power value of the machine).

Abstract: A visible-light activated photocatalyst N-doped TiO₂ nanocrystalline was synthesized via sonochemical method at low temperature. The N-doped anatase TiO₂ nanoparticles were prapared by sonication of the solution of tetrabutyl titanium and ammonium in water and ethanol at 70 °C for 150 min. The crystalline forms and crystallite sizes of the as-prepared sample is characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy and UV-Visible absorption spectrum.The product structure was dependent upon the reaction temperature and reaction time. The photocatalytic activity of the as-prepared photocatalyst was evaluated via the photodegradation of a basic dye methyl violet. The results show that the N-doped TiO₂ nanocrystalline prepared by sonication has an excellent photocatalytic activity under UV light and simulated sunlight.